/**
 * Welcome / landing screen.
 * - Node URL input with live ping + QR scanner
 * - Create / Import account buttons
 * Redirects to (app)/chats if key already loaded.
 */

import React, { useEffect, useState, useCallback } from 'react';
import {
  View, Text, TextInput, Pressable,
  ScrollView, Alert, ActivityIndicator,
} from 'react-native';
import { router } from 'expo-router';
import { CameraView, useCameraPermissions } from 'expo-camera';
import { useStore } from '@/lib/store';
import { saveSettings } from '@/lib/storage';
import { setNodeUrl, getNetStats } from '@/lib/api';
import { Button } from '@/components/ui/Button';

export default function WelcomeScreen() {
  const keyFile     = useStore(s => s.keyFile);
  const settings    = useStore(s => s.settings);
  const setSettings = useStore(s => s.setSettings);

  const [nodeInput, setNodeInput] = useState('');
  const [scanning,  setScanning]  = useState(false);
  const [checking,  setChecking]  = useState(false);
  const [nodeOk,    setNodeOk]    = useState<boolean | null>(null);

  const [permission, requestPermission] = useCameraPermissions();

  useEffect(() => {
    if (keyFile) router.replace('/(app)/chats');
  }, [keyFile]);

  useEffect(() => {
    setNodeInput(settings.nodeUrl);
  }, [settings.nodeUrl]);

  const applyNode = useCallback(async (url: string) => {
    const clean = url.trim().replace(/\/$/, '');
    if (!clean) return;
    setChecking(true);
    setNodeOk(null);
    setNodeUrl(clean);
    try {
      await getNetStats();
      setNodeOk(true);
      const next = { ...settings, nodeUrl: clean };
      setSettings(next);
      await saveSettings(next);
    } catch {
      setNodeOk(false);
    } finally {
      setChecking(false);
    }
  }, [settings, setSettings]);

  const onQrScanned = useCallback(({ data }: { data: string }) => {
    setScanning(false);
    let url = data.trim();
    try { const p = JSON.parse(url); if (p.nodeUrl) url = p.nodeUrl; } catch {}
    setNodeInput(url);
    applyNode(url);
  }, [applyNode]);

  const openScanner = async () => {
    if (!permission?.granted) {
      const { granted } = await requestPermission();
      if (!granted) {
        Alert.alert('Camera permission required', 'Allow camera access to scan QR codes.');
        return;
      }
    }
    setScanning(true);
  };

  // ── QR Scanner overlay ───────────────────────────────────────────────────
  if (scanning) {
    return (
      <View style={{ flex: 1, backgroundColor: '#000' }}>
        <CameraView
          style={{ flex: 1 }}
          facing="back"
          barcodeScannerSettings={{ barcodeTypes: ['qr'] }}
          onBarcodeScanned={onQrScanned}
        />
        <View style={{
          position: 'absolute', top: 0, left: 0, right: 0, bottom: 0,
          alignItems: 'center', justifyContent: 'center',
        }}>
          <View style={{
            width: 240, height: 240,
            borderWidth: 2, borderColor: 'white', borderRadius: 16,
          }} />
          <Text style={{ color: 'white', marginTop: 20, opacity: 0.8 }}>
            Point at a DChain node QR code
          </Text>
        </View>
        <Pressable
          onPress={() => setScanning(false)}
          style={{
            position: 'absolute', top: 56, left: 16,
            backgroundColor: 'rgba(0,0,0,0.6)', borderRadius: 20,
            paddingHorizontal: 16, paddingVertical: 8,
          }}
        >
          <Text style={{ color: 'white', fontSize: 16 }}>✕  Cancel</Text>
        </Pressable>
      </View>
    );
  }

  // ── Main screen ──────────────────────────────────────────────────────────
  const statusColor = nodeOk === true ? '#3fb950' : nodeOk === false ? '#f85149' : '#8b949e';

  return (
    <ScrollView
      style={{ flex: 1, backgroundColor: '#0d1117' }}
      contentContainerStyle={{ flexGrow: 1, paddingHorizontal: 24, paddingTop: 80, paddingBottom: 40 }}
      keyboardShouldPersistTaps="handled"
      keyboardDismissMode="on-drag"
    >
      {/* Logo ─ takes remaining space above, centered */}
      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center', gap: 16 }}>
        <View style={{
          width: 96, height: 96, borderRadius: 24,
          backgroundColor: '#2563eb', alignItems: 'center', justifyContent: 'center',
        }}>
          <Text style={{ fontSize: 48 }}>⛓</Text>
        </View>
        <Text style={{ color: '#fff', fontSize: 36, fontWeight: '700', letterSpacing: -1 }}>
          DChain
        </Text>
        <Text style={{ color: '#8b949e', textAlign: 'center', fontSize: 15, lineHeight: 22 }}>
          Decentralised E2E-encrypted messenger.{'\n'}Your keys. Your messages.
        </Text>
      </View>

      {/* Bottom section ─ node input + buttons */}
      <View style={{ gap: 12, marginTop: 40 }}>

        {/* Node URL label */}
        <Text style={{ color: '#8b949e', fontSize: 11, fontWeight: '600',
          textTransform: 'uppercase', letterSpacing: 1.2, marginBottom: 2 }}>
          Node URL
        </Text>

        {/* Input row */}
        <View style={{ flexDirection: 'row', gap: 8 }}>
          <View style={{
            flex: 1, flexDirection: 'row', alignItems: 'center',
            backgroundColor: '#21262d', borderWidth: 1, borderColor: '#30363d',
            borderRadius: 12, paddingHorizontal: 12, gap: 8,
          }}>
            {/* Status dot */}
            <View style={{ width: 8, height: 8, borderRadius: 4, backgroundColor: statusColor }} />

            <TextInput
              value={nodeInput}
              onChangeText={t => { setNodeInput(t); setNodeOk(null); }}
              onEndEditing={() => applyNode(nodeInput)}
              onSubmitEditing={() => applyNode(nodeInput)}
              placeholder="http://192.168.1.10:8081"
              placeholderTextColor="#8b949e"
              autoCapitalize="none"
              autoCorrect={false}
              keyboardType="url"
              returnKeyType="done"
              style={{ flex: 1, color: '#fff', fontSize: 14, paddingVertical: 14 }}
            />

            {checking
              ? <ActivityIndicator size="small" color="#8b949e" />
              : nodeOk === true
                ? <Text style={{ color: '#3fb950', fontSize: 16 }}>✓</Text>
                : nodeOk === false
                  ? <Text style={{ color: '#f85149', fontSize: 14 }}>✗</Text>
                  : null
            }
          </View>

          {/* QR button */}
          <Pressable
            onPress={openScanner}
            style={({ pressed }) => ({
              width: 48, alignItems: 'center', justifyContent: 'center',
              backgroundColor: '#21262d', borderWidth: 1, borderColor: '#30363d',
              borderRadius: 12, opacity: pressed ? 0.7 : 1,
            })}
          >
            <Text style={{ fontSize: 22 }}>▦</Text>
          </Pressable>
        </View>

        {/* Status text */}
        {nodeOk === true && (
          <Text style={{ color: '#3fb950', fontSize: 12, marginTop: -4 }}>
            ✓ Node connected
          </Text>
        )}
        {nodeOk === false && (
          <Text style={{ color: '#f85149', fontSize: 12, marginTop: -4 }}>
            ✗ Cannot reach node — check URL and that the node is running
          </Text>
        )}

        {/* Buttons */}
        <View style={{ gap: 10, marginTop: 4 }}>
          <Button size="lg" onPress={() => router.push('/(auth)/create')}>
            Create New Account
          </Button>
          <Button variant="outline" size="lg" onPress={() => router.push('/(auth)/import')}>
            Import Existing Key
          </Button>
        </View>
      </View>
    </ScrollView>
  );
}